Field of the Invention
The invention relates to a control device for an electrically-driven vacuum pump for generating a negative pressure in a negative pressure chamber of a brake booster of a vehicle.
Description of the Related Art
Conventionally, there is known a brake booster operated by a negative pressure generated by an electrically-driven vacuum pump. A control device for the electrically-driven vacuum pump is described in Unexamined Japanese Patent Publication No. 63-212162. The control device controls operation of the vacuum pump to keep a sufficient negative pressure in the brake booster. This control device starts the operation of the vacuum pump when the state of the brake device changes from an operating state to a non-operating state.
On the other hand, the control device stops the operation of the vacuum pump when the negative pressure in the brake booster detected by a negative pressure sensor becomes larger than or equal to an upper limit set value. Thereby, even when the decrease of the negative pressure in the brake booster is small to the extent that a negative pressure switch is not operate, the vacuum pump is certainly started to be operated. Thus, the shortage of a braking force is prevented from occurring. Note that the term “negative pressure” means a magnitude of the negative pressure in this specification and the claims.